1. Field of the Invention
The present invention relates to a lock control device for vehicles, and more particularly to a lock control device for vehicles which prevents an unauthorized entry into a vehicle and the unauthorized use of the vehicle by a third party.
2. Description of the Prior Art
In a conventional lock control apparatus, a door lock device holds the door closed by engaging a door lock mechanism attached to the door with a striker attached to a vehicle body. When an inside handle or an outside handle is released, a panel of the door lock mechanism is unlatched and the door is opened by disengaging the door lock mechanism and the striker. The door lock mechanism has a lock function for preventing the opening of the panel when the inside handle or the outside handle is released. A key cylinder attached to the door and a lock knob attached within the vehicle are connected to the door lock mechanism through a link and the door lock mechanism is locked or unlocked according to the operation thereof.
In this conventional lock control apparatus, however, the key cylinder is connected to the door lock mechanism through the link, so that when the link is actuated the door lock mechanism is unlocked and the door can be opened by the operation of the outside handle. Further, in an engine ignition circuit, an outer portion of an engine key switch may be shorted by an electric lead line and the engine can be easily started.
There has been a proposal for a door lock in which an unlock code and a lock code are sent by a transmitter and received by the lock mechanism. The door lock is a coincidence type lock that unlocks the door lock mechanism only when the unlock code is received. An example of such an mechanism may be found in Japanese application publication nos. 57(1982)-7737 and 59(1984)-24075). In that lock control apparatus, when a car owner sends an electrical signal from outside the vehicle and the door is unlocked, it is possible for a third party to receive the unlock code, analyze the unlock code, and make a transmitter for sending a similar unlock code. The transmitter is in effect similar to a duplicate key. When the car owner is absent, the bogus transmitter may be used to break into the car.
Further, a conventional lock knob is provided on each door within the vehicle to indicate whether the vehicle is locked or unlocked and to enable the door to be locked or unlocked from within the vehicle. The lock knob can be manually operated after breaking the window so that the lock system is not secure.